Liquid contact switch



7, 1937- v J. H. PAYNE, JR

LIQUID CONTACT SWITCH Filed Dec. 28, 1934 Inventor: John i'LFagne J11,

I 77 Damian by fil i Attorneg.

Patented Dec. 7; 1937 "UNITED STATES L QUID CONTACT SWITCH John H. Payne, Jr.,

to General Electric Company,

New York Ballston Spa, N. Y., assignor a corporation of Application December 28, 1934, Serial No. 759,527

Claims.

The present invention relates. to mercury switches and has for its object the provision of a rugged, low-resistance switch which is particularly well adapted for quantity production by 5 automatic machinery.

While mercury switches of the type-provided with inlead conductors sealed in a glass envelope have been satisfactory, their cost has been relatively high due to inherent difficulties of.

their fabrication and the required size of the switch for a given current rating. Furthermore, as flexible conductors must be attached to the inlead conductors and separate mounting means must be providedfor the switch, the cost of the switch as a whole thereby is further increased.

In mercury switches embodying my invention a pair of electrically conducting metal wall members are electrically insulated from one another and hermetically sealed to one another by means of a relatively thin layer of glass, or suitable thermo-plastic sealing material, which when fused becomes united with the metal members.

In this manner a switch container consisting almost wholly of metal is produced which requires no leading-in conductors and which is capable of being mounted upon current supply conductors which engage said metal members and form bearings on which the switch may be rotated. In some cases the wall members are substantially 3o hemi-spherical so that a. substantially spherical gas-tight container is formed by the joining of the two members. A body of mercury within the container is arranged to make and break an electrical circuit between the metal wall members. While mercury is usedcommonly it is to understood that other liquid metals may be used, as for example gallium.

Though not limited thereto my invention is particularly adapted to the control of lamps,

motors, heaters and other industrial and domestic devices which are operated with substantial currents.

One of the advantages of the switch of the present invention is its low electrical resistance, 5 due to its construction, small size, and the elim-' ination of leading-in conductors.

At the present time switches constructed in accordance with the present invention have operated many million times without failure or damage to the switches.

The above and other novel features of my invention are explained in greater detail in the following description in connection with the accompanying drawing and are set forth with particularity in the appended claims.

In this drawing Fig. 1 is a side elevational view of the switch shown in Figs. 5 and 6 mounted in a housing which is set in a recess in a support, the housing and support being shown in section; Fig. 2 is another view of the same switch assembly taken at right angles to Fig. 1, the wall support being omitted; Figs. 3 to 7 and 11 are sectional views of various types of switches embodying my invention; Fig. 8 is a sectional view of a part of the apparatus for fabricatingsuch a switch; Fig. '9 is a perspective view on a smaller scale of a switch in process of fabricationheld,

by rotating spindles, one of which is shown on an enlarged scale in Fig. 8; and Fig. 10 is a sectional view of a switch of Fig. 11 in process of fabrication.

In the preferred forms of Figs. 5 to 7 and 11, two dished or concave metal members I, 2 are assembled in juxtaposition with an apertured disc 3 of suitable refractory material held therebetween. These members should consist of metal which will be wetted by the glass, or other thermo-plastic material. For example, chromeiron or nickel-iron alloys may be used, or'alloys of iron, nickel and cobalt. I have used with good success an alloy of iron and chromium, the latter forming about 26 to '30 per cent of the alloy.

- The structures using the chrome-iron alloys are claimed in my co-pending application, Serial No. 163,489, filed September 11, 1937, and asign ed to the same assignee. The disc 3 may consist of magnesia, alumina, thoria, zirconia, orother refractory oxide or mixtures thereof, a material being desired which may be subjected without deterioration to the arc resulting upon the break of a circuit. Preferably the refractory material should be chosen to have substantially the same coefiicient of thermal expansion as adjoining parts and to be capable of being wetted by the thermo-plastic sealing material. When using ordinary lead glass and ferro-chrome metal parts I have used with success a mixture of about to per cent of magnesia and 25 to 20 per cent of clay. The disc 3 has an aperture 4 which is located oil-center so that a body of mercury 5 in the switch will connect electrically the wall members I, 2 in one position of the switch as shown in Fig. 6. Upon rotation of the switch about an axis a, b shown in dotted lines in Fig. 6, the disk 3 will operate to interrupt the electrical continuity of the mercury, the break 00- curing in the aperture 4. Means for rotationally: mounting such a switch is shown in Figs. 1 and 2 e which will be later described. In Fig. 5 the aperture 4 is shown above the level of the mercury,

the circuit through the switch being open. When the wall members I, 2 and the disc 3 are assembled in the position shown, a sealing member of suitable material is caused to become welded to the flanged rims 6 and I, of the wall members I, 2 as best shown at 8 in Fig. 6. When sealing chrome-iron alloy parts, I may use lead glass or lime glass, the glass being chosen to have substantially the same coeflicient of thermal expansion as the alloy. The glass seal or weld may be produced in various ways. For example, a glass fillet '8 may be deposited as shown in Fig. 9 by supporting the assembled wall members between rotatable spindles 9, land causing glass in a plastic condition to be wound as a partially fused rod about the rims of the wall members.v The glass may be fed from a source (not shown) which supplies a thin glass rod or cane I I through a guide I2 to the rims of the wall members. The latter are held in desired position pressed against the periphery of the disc 3. The glass cane I I is fed downwardly at a rate of speed which is substantially the same as the rotational speed of the assembled parts. Theglass is softened by the flames playing thereon from burners I3, I4 and I 5, I6.

One of the wall members of the switch is provided. with an aperture modification of Fig. 7. When the wall members are being sealed together and are held and rotated by the spindles 9, I0, as shown in Fig. 9, a fine needle-like nozzle I9 (Fig. 8) projects into this opening and supplies a suitable gas, such as hydrogen, to the interior of the container formed by the two wall members. The nozzle I9 being connected to a duct 20 in the interior of the spindle I at the end of which the wall member 2 is held, the gas being supplied through the duct 26. The space between the duct 20 and the hollow spindle I0 preferably is evacuated through a conduit M which passes through a fixed member 22 of the apparatus (shown broken away). The spindle I0 (with the collar 23 mounted thereon) is rotated by any suitable means (not shown) in synchronism with the spindle 9, the members I and 2 being held between them firmly by suction. Although hydrogen is supplied to the interior of the matched members I, 2 a sub-atmospheric pressure (partial vacuum) exists therein due to the loose fit of the needle I9 and the vacuum in the spindle I 0. The vacuum assists the fusing on of the glass to make a gas-tight seal.

The fillet 8 of glass, or other suitable thermoplastic sealingmaterial is welded to' the rims 6 and I and may project above them as shown in Figs. and 6. The glass also is welded to the disc 3 thereby holding it firmly in desired position within the switch.

The anchoring and sealing fillet of glass, or other sealing material, may be applied to the assembled switch members as an encircling ring 24, as shown in Fig. 10. When the ring 24 is softened, as by the heat of gas flames (not shown) playing thereon, then the plastic glass is drawn by suction into desired position to seal and weld to the switch members including the diaphragm as shown in Fig. 11. The partial vacuum within the switch housing causes the plastic glass to be pulled into proper relation with the edges of the wall members I 2 even though the ring 24 is not perfectly aligned with the wall members.

When the sealing operation is finished a quanas shown at I8 in the tity of mercury is introduced through the aperture I8 into the container through the nozzle I9. The aperture I8 finally is sealed by a small tacklike sealing member-25, as shown in Figs. 3 to 6. The seal 25 may be inserted with the mercury in position covering the opening I8 to prevent the escape of the gas filling. Finally the sealing I member may .be electrically welded to the container to make a permanent gas-tight closure. After the switch is sealed current is passed through it and it is rotated in such manner as to cause an arc to occur between the wall members I, 2 and the mercury. This breaks down any film of oxide on the members I, 2 and materially lowers the resistance of the switch.

In case the introduction of the mercury occurs by a subsequent factory operation, then it is de-- sirable that the switch container shall be reheated and reexhausted before being charged with mercury and hydrogen.

The method of manufacture set forth in the foregoing is fully described and claimed in my co-pending application, Serial Number 118,828, filed November 20, 1936 and assigned to the General Electric Company.

It is not necessary inall cases that a diaphragm of refractory material, such as shown at 3 of Figs. 5 and 6, should be used although its use is recommended in order to operate the switch with a mercury-to-mercury break. In some cases, as shown in Figs. 3 and 4, the two wall members I, 2 are joined to one another by an intermediate glass sealing member which has such a large aperture that the break in the mer cury must be brought about by tilting the switch as shown in Fig. 3 instead of rotating the switch as shown in Figs. 5 and 6. Due to the high surface tension of the mercury the tilt of the switch will not with all cases cause the mercury to separate into two portions with the circuit break in the mercury. The mercury may flow over the ring 2'! (which acts as a dam) so that the arc in the switch occurs between the mercury and one of the wall members. While switches of this construction have been operating successfully with over 30 millions of circuit-making and -breaking operations, I prefer to use the construction of Figs. 5 and 6 especially for high currents.

Because of their small size, large contact surfaces, and the presence of a reducing gas, such as hydrogen, switches made in accordance with my invention have an extraordinarily low internal electrical resistivity. The resistivity commonly is about .001 to .0005 ohm or even lower. Their current-carrying capacity is high relative to their size. A switch about one-half inch in diameter is suitable for carrying and breaking currents of about twenty amperes.

In the structures shown in Figs. 3 and 4 the glass sealing member 21 may be a preformedannular disc which is placed in the position shown upon one of the hemispherical wall members. When in this position the glass is softened by a flame or by any other suitable application of heat and then the second hemispherical wall member is brought with its flanged rim 28 in abutting relation to the softened periphery of the glass joining the flanged rim 29 of the wall member I and a weld is produced between the glass and the juxtaposed wall members by the application of pressure. Upon hardening of the glass a strong unitary spherical container is produced, the rims of the two hemispherical wall members being hermetically sealed to one another. In this case the introduction of mercury and hydrogen also occurs through an opening which is later sealed as described in connection with Figs. 5 and 6.

While in Figs. 3 to 6 the wall members I, 2 have been shown as being hemispherical,it should be understood that my invention is not limited to any particular configuration of wall members or diaphragm. Fig. '7 illustrates a modification in which angular wall members 30, 3| are used, these being provided with raised bosses 32 to facilitate mounting of the switch. The diaphragm 33 in this modification has a peripheral flange 35 which, as shown, is pressed against the wall members 30: 3!.

Figs. 1 and 2 show for illustrative purposes a suitable mounting for a switch embodying my invention. The switch is held within an insulating housing 36 by spring clips 31, 38 which are connected to electric terminals 39, 40. Surrounding the periphery of the switch is a frame 4| to which is attached a handle 42. The housing is closed by a face plate 43 which is held in position on the supporting structure 44 by the screws 45. When the handle 42 is moved through an arc the switch is rotated sufficiently to result in making, or completing, a circuit in one position and breaking the circuit in another position.

The small size of switches embodying my invention and the fact that no lead-in conductors are required renders them adaptable for types of service (as for example the above-described wall switch) for which former types of mercury switches are not well suited. Furthermore, switches in accordance with the present invention can be replaced without disconnecting conductors since the switch is resiliently held between spring clips. The insertion of a switch between the clips automatically completes the circuit to the electrodes and wall members of the switch. For convenience, the term mercury switch as used in'the present specification and claims is defined as a switch which employs a conducting liquid to make and break an electrical circuit.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

I. An electric switch comprising the combination of a plurality of dished metal members shaped to form an enclosure, an apertured partition of arc-resisting material interposed between said members and spacing them apart, a fillet of glass sealed to said members and to said partition at the peripheral edges thereof for hermetically sealing the enclosure formed by said members, and a body of liquid conducting material in said enclosure whereby electrical circuit between said members may be made and broken.

2. An electric switch comprising a pair of dished metal receptacles of circular outline juxtaposed breaking a circuit between said metal receptacles.

3. An electric switch comprising the combination of a plurality of dished metal members shaped to form an enclosure, an apertured partition of arc-resisting materialinterposed between said members and spacing themapart, said partition being completely shielded from the external atmosphere by a fillet of glass which is fused to said members and in continuous contact with the periphery of said partition whereby said fillet forms both an hermetical seal between said members and a mercury tight joint between said par .tition and each of said members, and a body of liquid conducting material in said enclosure whereby electrical circuit between said members may be made and broken through the aperture in.

said partition.

4. An electric switch comprising a pair of juxtaposed dished metal members shaped to form an enclosure, substantially radially exending peripheral flanges on said dished members, a circumferential fillet of glass interposed between said flanges and sealed in extensive surface contact with the opposed faces thereof, an apertured insulating barrier forming a partition between said dished members, the outer periphery of said barrier being in continuous contact with said glass fillet whereby it is completely shielded from the external atmosphere, and a quantity of mercury in said enclosure for making and breaking a circuit between said dished members.

5. An electric switch comprising a'pair of jux-- taposed dished metal members shaped to form an enclosure, substantially parallel peripheral flanges on said dished members, a circumferential strip of fusible vitreous material sealed between said flanges and in extensive contact with the opposed tween.

JOHN H. PAYNE, JR. 

